The latest version of the extremely popular Lambretta LD was presented to the press on the 2nd of February 1957 in the well-lit rooms of the Centro Studi area of the Innocenti factory. The two hostesses to launch the new model were film starlets Edy Campagnoli and Marisa Borroni.

During the introduction, the engineer and sales director Tomasi traced the entire sales records for the almost ten years of Innocentis lead of the scooter world. At this point, more than one million units had been produced, of which 200,000 were exported around the world. More than 4,000 working machines to produce these vehicles were set up in the Innocenti industrial complex. The entire factory area measured one million square meters, all under the management of the president of the company, Ferdinando Innocenti.

With the nickname "57", the LD would be the last shaft-driven Lambretta with dual cores produced, a design which stemmed from the very first Lambretta 125 A. Afterwards, Innocenti preferred the more simple and economic system of a chain-driven transmission sealed in oil. The new LD 57 had the advantage of numerous mechanical and esthetic improvements, which made it an exceptionally reliable and elegant scooter. One important modification concerned the starter, which was completely redesigned using a epicyclical wheel with cylindrical gears that improved the ratio between the range of the kickstarter and the rotation of the motor. This new mechanical piece together with the larger kickstarter resolved once and for all the starting problems of the LD, which up until that point never worked well.

Another interesting mechanical innovation on the LD was the air intake for the carburetor placed under the rear seat. This allowed the air to enter a small chamber before hitting the air filter and helped to diminish the obnoxious noise of the carburetor typical on the older models. The last but not least important of the improvements were a covering over the drum brakes to prevent them from getting dirty and a longer tube at the end of the muffler to further distance the motor from the exhaust.

The most noticeable modifications to the bodywork were the handlebars and the glovebox. The former was improved with an elegant aluminum finish that now contained the tachometer and the horn. The glovebox was shifted from behind the front legshield to behind the rear saddle and was incorporated into the frame. The electrical system was improved as well with better working and more efficient electrical switches, a larger taillight, and a chrome anti-reflective "hood" on the front headlamp. The 150cc version was offered by Innocenti on the Italian market in an elegant two-tone paint scheme.

The base color of the scooter was still light gray, but the buyer could choose the color of the side panels, horn cover, and handlebars between: blue, red, beige, and green.

On the electric-starting version, the battery was placed in the now-useless rear compartment, so an extra glovebox was added behind the front legshield, like on the previous 150 LD model. The Lambretta 150 LD with electric start was only built for a few months, totaling 4,000 units mostly for the foreign market. Only 52 of the 125 LDs were built with an electric starter probably for an important foreign dealer. The extremely low demand for the model with an electric starter convinced Innocenti not to offer it again as an accessory on the LD. Production of the LD 57 ceased for good in July of 1958 after a total of 160,000 units had been produced of the two-sized scooters.

During the last period of production, Innocenti prepared a small number of unassembled LD motors to send to India in an effort to begin production of the first Lambrettas built under license in the Far East.